Her fans, and they are many, call her “La Divina,” the divine one, and “Maria By Callas” shows the reasons why.

Closer to a deity than a singer to her devotees, Maria Callas was an extraordinary opera star who brought dramatic intensity and emotional intelligence to her roles, not to mention an off-stage life that included a much-publicized love affair with one of the world’s wealthiest men, fellow Greek Aristotle Onassis.

Leonard Bernstein called Callas “pure electricity.” Eager admirers would unhesitatingly camp out overnight when tickets for her performances went on sale. Everything she did made newspaper headlines. But who was she, and what was it like to be in her presence?

Director Tom Volf initially planned to do a conventional documentary to answer these questions, and in fact spent a year interviewing some 30 friends of the great diva, who died in 1977 at age 53.

Instead Volf decided it would be more intimate and revealing to do a film on Callas almost entirely in her own words, using performance footage, TV interviews and home movies as well as letters and unpublished memoirs movingly read by contemporary opera luminary Joyce DiDonato.

The result actually works as Volf planned. While “Maria By Callas” is short on facts and biographical detail, it expertly presents an emotional essence of this performer, leaving you both shaken and stirred by the extent of her gifts and the way they connected to both audiences and her tumultuous life.

A first-time filmmaker but known as a photographer, Volf made good on a number of risky production choices that enhanced the effects he sought.

Rather than inundate viewers with a hoard of snippets, Volf presents several arias filmed in their entirety. These include a 1958 performance of Callas’ signature aria, “Casta Diva” from Bellini’s “Norma,” and an aria from Puccini’s “Tosca” that expressed her personal philosophy: “Vissi d’arte, Vissi d’amore,” I lived for art, I lived for love.

When he discovered color photographs of performances, as Volf did with that “Norma” aria, the director has delicately colorized the black-and-white footage to match. Similarly, his decision to show the sprocket holes and frames of original 8 mm home movies effectively enhances the sense of time past.

Volf has been persuasive in his contacts with Callas’ inner circle, getting not only that 8 mm footage but also unearthing a copy, saved by the diva’s butler, of a 1970 interview Callas gave to David Frost that was thought to be lost.

That conversation is in depth enough for Volk to use it as his documentary’s spine, returning to it again and again for Callas’ candid comments on key aspects of her life.

Born of Greek parents in New York, Callas and her family were caught in Greece during World War II, where her musical training began. The film features a charming interview with Callas’ teacher, Elvira de Hidaldo, who remembers her student as a hard worker with a formidable drive.

Despite her great gifts, Callas as an adult felt she had been pushed too hard into having an operatic career, first by her domineering mother and then by her husband, Giovanni Battista Meneghini.

She would have happily given it all up to have children and a domestic existence, Callas informed a dubious Frost, adding “but destiny is destiny and there is no way out.”

That conflict between personal and professional personas was key, Callas felt, to her life. “There are two people in me actually; there is Maria but also Callas,” she told Frost. “I have to live up to all of myself.”

Because its structure is tied to Callas’ on-the-record words, not all the issues of her life are dealt with in the documentary. But it does go into detail about her most celebrated professional scandal, when illness caused her to cancel the second half of a performance in Rome, and the disbelieving media, active even before internet trolls, pilloried her unmercifully. “My lynching,” she says tartly, “had begun.”

“Maria by Callas” also deals extensively with the married singer’s long romance with the equally married Onassis and her total shock when he threw her over to marry Jackie Kennedy.

DiDonato is especially strong reading the letters from this period. “I am so lost,” Callas wrote when she got the news, though the two eventually reconciled. “Our affair was a failure,” she explains, “but our friendship was a success.”

“I have done everything honestly,” Callas summed up to Frost. “I cannot learn the art of being a hypocrite.” Her fans wouldn’t have it any other way.